Printing differences are probably from there being different print runs as the summer went on, or from the packaging being printed at different printing plants.
While these aren't from 75, they show the packing plant information that's on the hidden side panel of the boxes.
Most of the info there explains itself. Natick was a packing plant local to me at the time. (Sort of, local from late 77 - 83 anyway..) The CT1933 is a Connecticut license number that's on a lot of food products sold in CT. 1933 would be specific to Hostess, possibly to the Natick plant. I haven't figured out the ING numbers. They might be job numbers that Hostess could relate to orders to the printer, but that's just a guess.
Steve B